Physiological tone control circuit



Oct. 27, 1953 H. A. BRoos 2,657,363

PHYSIOLOGICAL TONE CONTROL CIRCUIT Filed July 12, 1949 E; 6 if 7 2 E?- 1- a j .50 d I was; 29 Y 6 72 INV EN TOR. HEMQZUUJADBIANMYBROO/S'.

Patented Oct. 27, 1953 2,657,363 PHYSIOLOGICAL TONE CONTROL CIRCUIT Henricus Adrianus Broos, Eindhoven, Netherlands, assignor to Hartford National Bank and Trust Company, Hartford, Conn as trustee Application July 12, 1949, Serial No. 104,334

In the Netherlands August 7, 1948 3 Claims. (Cl. 333+70) This invention relates to. circuits for the. so.- called physiological amplification .of lowz-fres quency oscillations, for example, for use in. the lowefrequency amplifying part of a radioereceiver. The term physiological amplification means that. the input circuit of the amplifying circuit. comprises a gain control controlling. the amplification factor, whereby at a low volume setting of the gain control, the low-tone frequencies are emphasized relatively to the intermediate tone frequencies (low-tone physiology), or the high-tone frequencies are emphasized rela.- tively to the intermediate tone frequencies (hightone physiology).

Low-tone physiology is usually obtained with the use .of a gain control having a top contact, a bottom contact and also a third fixedicontact, the part of the gain control between the third fixed contact and the bottom being shunted by a network which passes intermediate and hightone frequencies.

High-tone physiology may, for example, be obtained by connecting the top of the gain control to the moving contact through a filter which passes high-tone frequencies. The disadvantage of a. circuit having a lowand. high-tone physiology combined in this manner is that the low.- tone physiology .is no longer varied when the moving contact of the gain control moves beyond the third fixed contact, whereas the hightone physiology still continuously increases when the moving contact is moved downwards. For example, with the use of a fourth fixed contact and asecond networkwhich passes the intermediate and high tones, a slight amount of lowtone physiology may even be obtained beyond the third fixed contact, but this results in an unsatisfactory controlwhich is not particularly smooth. It is also costly to manufacture a gain control having severaltappings.

This invention has for its object to minimise the. said disadvantage in a simpleway. According to the invention, provision is made ofn'ot' only the said 'lowand high-tone physiology but also of a connection-between the moving contact ,of the gain control, and a network which ensures low-.tonecphysiology. More particularly,

the connection bringing about the additional w- In order that the invention may be more clear ly understood and readily carried into effect, two embodiments will now be described by way of example with reference to the accompanying drawing, of which:

Fig. 1 shows a schematic diagram of one form and Fig. 2 shows a more elaborated form of the invention.

In Fig. 1, an amplifying tube 1 i shown, the inp t circuit of which comprises a gain control 4 having two terminal contacts H and I: and also a third fixed contact I2. The gain control i has supplied to it between the top I? and the bottom H the oscillations to be amplified, the amplification of the circuit being controllable by a moving contact .6. The third fixed contact l2 and the bottom ll of the gain control have connected between them a filter network which passes the intermediate and high-tone frequencies and provides the low-tone physiology. In the present example this consists of a series combination of a resistance and a capacity It, it. The high-tone physiology is provided by a network I8, I 9 which only passes high-tone frequen cies and which is connected between the top H and the moving contact 5 of the gain control.

If the moving contact 6 moves downwards, both the low and the high tones will be more and more emphasized relatively to the'intermediatetone frequencies. The disadvantage of a circuit comprising onl the elements described so far, is that beyond the fixed contact i2 there is no further emphasis of the low tones, whereas the emphasis of the high tones still continuously increases. According to one form of the invention, an additional connection maybe provided between the moving contact 6 and a network which ensures low-tone physiology. Such a network may, for example, consist of the series-combination of a resistance and a capacity, arranged in parallel with the gain control 4 and connected, for example, to the top I! and the bottom M respectively.

According to the form of the invention shown in Fig r 3 W 7 mple on i found by connecting the junction of resistance It" and ondenser t of th net rk sur ng low-tom? physiology through a resistance ll to themov ing contact 6.

In the more elaborate circuit-arrangement shown in Fig.2, in which the same reference numerals designate corresponding circuit elemen-ts to those of Fig. l of the accompanying drawings and of the drawing accompanying my co-pending patent application Serial No. 104,335, filed July 12, 1949, now Patent No. 2,591,915, issued April 8, 1952 the bottom of the gain control is connected to a source of negative feedback voltage, constituted by a tap c-e of the secondary winding IE3 or" an output transformer 3 included in the output circuit of the discharge tube 1, the top H of the gain control being connected through impedances i i and 26 to a source of positive feedback voltage, constituted by a tap c-d of the secondary winding iii. The resistances of gain control 4 and of impedances l4 and 2d are chosen to be such that substantially no negative feedback or only small negative feedback is operative at the top of gain control 4, whereas strong negative feedback is operative at the bottom of gain control t. A so-called loss-free negative feedback of the circuit is thus ensured in known manner. Furthermore impedances I3, 14 are provided in combination with impedances l5, 16, so that strong negative feedback of the intermediate tone frequencies occurs at the level of the third fixed contact i2 of the gain control cl. The filter i8, is which ensures high-tone physiology is connected, for example, between the moving contact and the junction of the resistances Hi and As described in my said copending U. S. patent application, the impedances it may be shunted by a resistance st and be con ected to a source of negative feedback voltage c-b, which is substantially of the same order of magnitude as the source of positive feedback voitage c--d. The source c-e of negative feedback voltage connected to the bottom ii of gain control is then larger than the source 0-13, and the impedance between tap b and the third i red contact i2 is chosen to be small with respect to the resistance of that part of the gain control located between the third fixed contact if and the bottom ii. As describedin the said copending application, these measures ensure a noiseless physiological control. It is here advisable to avoid, by the use of a blocking condenser d2, connected for example in series with resistance at or, if desired, in series with resistance It, the flow of direct current through the circuit of the moving contact 8.

What I claim is:

l. A circuit arrangement for amplifying an input signal having high, medium and low frequency components, comprising an amplifier stage having an input circuit, and means to apply said signal to said input circuit and to vary the amplitude thereof, said means also varying the relative strength of said frequency components and comprising a potentiometer element having top, bottom and intermediate fixed contacts and a movable gain control contact, means to apply said signal between said top and bottom contacts, means to couple said movable contact and said bottom contact to said input circuit thereby to apply said signal to said input circuit, a first impedance network adapted to pass said high frequency components intercoupling said movable contact and one of said top and intermediate contacts thereby to emphasize said high frequency components with respect to said medium frequency components for positions of said movable gain control contact between said top and bottom contacts, a second impedance net- Work adapted to by-pass said high and, medium frequency components intercoupling said intermediate fixed contact and said bottom contact thereby to emphasize said low frequency comable contact and said second impedance network to increase the emphasis of said low frequency components with respect to said medium fre-' quency components when said movable gain con-' trol contact is positioned between said intermediate fixed contact and said bottom contact.

2.1%. circuit arrangement for amplifying an input signal having high, medium and low fre-- quency components, comprising an amplifier stage having an input circuit and means to apply said signal to said input circuit and to vary the amplitude thereof, said means also varying the relative strength of said frequency components and comprising a potentiometer element having top, bottom and intermediate fixed contacts and a movable gain control contact, means to apply said signal between said top and bottom contacts, means to couple said movable contact and said bottom contact to said input circuit thereby to apply said signal to said input circuit, a first impedance network adapted to pass said high frequency components inter-coupling said top and movable contacts thereby to emphasize said high frequency components with respect to said medium frequency components for positions of said movable gain control contact between said top and bottom contacts, a second impedance network adapted to by-pass said high and medium frequency components intercoupling said intermediate contact and said bottom contact thereby to emphasize said low frequency components when said movable gain control contact positioned between said top and intermediate contacts and means to increase the emphasis of said low frequency components with respect to said medium frequency components when said movable gain control contact is positioned between said intermediate fixed contact and said bottom contact comprising a resistance element interconnecting said second impedance network and said movable contact.

3. A circuit arrangement for amplifyin an input signal having high, medium and low frequency components, comprising an amplifier stage having an input circuit, and means to apply said signal to said input circuit and to vary the amplitude thereof, said means also varying the relative strength of said frequency components and comprising a potentiometer element having top, bottom and intermediate fixed contacts and a movable gain control contact, means to apply said signal between said top and bottom contacts, means to couple said movable contact and said bottom contact to said input circuit thereby to apply said signal to said input circuit, a first impedance network adapted to pass said high frequency components intercoupling said top and movable contacts thereby to emphasize said high frequency components with respect tosaid medium frequency components for positions of said movable gain control contact between said top and bottom contacts, a second impedance network adapted to by-pass said high and medium frequency components and comprising a first resistance element and a capacitive element connected in series, said series combination intercoupling said intermediate fixed contact and said bottom contact thereby to emphasize said low frequency components when said movable gain control contact is positioned between said top and intermediate contacts and means to increase the emphasis of said low frequency components with respect to said medium Number Name Date frequency components when said movable gain 2,037,753 Barton Apr. 21, 1936 control contact is positioned between said inter- 2,037,842 Wolff Apr. 21, 1936 mediate fixed contact and said bottom contact 2,043,161 Foster June 2, 1936 comprising a second resistance element inter- 5 2,317,025 Bond Apr. 20, 1943 connecting the junction of said first resistance 2,322,558 Bachman June 22, 1943 element and said capacitive element and said 2,352,931 Austin July 4, 1944 movable contact. 2,361,602 Clark Oct. 31, 1944 Min r Mar- 6 References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,997,762 Bierwirth Apr. 16, 1935 15 

